1. Field of the Invention
This invention relates to pellet durability testing. In one aspect, the invention relates to a device for testing the durability of pellets while in another aspect, the invention relates to a method of testing the durability of pellets, particularly uncured pellets.
2. Description of the Prior Art
Pellets, here defined as an agglomeration (however formed, e.g. by pellet mill, extruder, etc.) of individual ingredients (typically ground ingredients), or a mixture of such ingredients or their equivalents, are a convenient form for a variety of products, e.g. animal feeds, -pharmaceuticals, dietary supplements, water treatments, etc. Pellets offer ease of handling from manufacture through consumption, and allow considerable freedom in functional design, e.g. nutritional composition, size, shape, and the like.
Because pellets are usually subjected to a considerable amount of jostling from the time of their manufacture to the time of their ultimate consumption or use, and because many end uses require or have a preference for pellets with good structural integrity, such as many dry animal feed products, durability is an important physical property of the pellet. Durability, i.e. the resistance of a pellet to significant deterioration over time, can be measured by a variety of different tests, the K-State Pellet Quality Test for animal feed products being representative. This test is described in detail at pages 528-9 of Section 6 of Appendix F to Feed Manufacturing Technology, published by the Feed Production Council of the American Feed Manufacturers Association (1976). While this and similar tests provide a useful durability measure for a pellet, here an animal feed pellet, the principal disadvantage of these tests are that they are performed on cured pellets, i.e. pellets that have been collected, dried, cooled and/or screened. By the time these steps have been completed, a production run, often measured in tons of product, has been completed and if the pellet durability is poor, then the pellets of that production run must either be reprocessed or disposed as off-specification product. This is particularly true of extruded pellets where considerable time can elapse between pellet formation, usually at elevated temperature, pressure and water content (an uncured state), and the measurement of durability of a hard, dry pellet (finished product or cured state).
As such, the determination of pellet durability is most desirably made shortly after the pellet is formed such that if the durability of the pellet is found to be poor, then one or more process parameters, such as increasing or decreasing the amount of binder, steam, compaction pressure, etc., can be adjusted immediately to bring pellet durability into compliance with a desired specification. Such an on-line testing device should be able to perform the test quickly, efficiently and repeatedly over the course of a production run. In addition, the testing device should be readily adaptable to existing pellet manufacturing equipment and procedures.